The Magma Chamber Simulator (MCS) is a thermodynamic tool for modeling the evolution of magmatic systems that are open with respect to assimilation of partial melts or stoped blocks, magma recharge + mixing, and fractional crystallization. MCS is available for both PC and Mac. In the MCS, the thermal, mass, and compositional evolution of a multicomponent–multiphase composite system of resident magma, wallrock, and recharge reservoirs is tracked by rigorous self-consistent thermodynamic modeling. A Recharge–Assimilation (Assimilated partial melt or Stoped blocks)–Fractional Crystallization (RnASnFC; ntot ≤ 30) scenario is computed by minimization or maximization of appropriate thermodynamic potentials using the family of rhyolite- and pMELTS engines coupled to an Excel Visual Basic interface. In MCS, during isobaric cooling and crystallization, resident magma thermally interacts with wallrock that is in internal thermodynamic equilibrium. Wallrock partial melt above a user-defined percolation threshold is homogenized (i.e., brought in to chemical potential equilibrium) with resident magma. Crystals that form become part of a cumulate reservoir that remains thermally connected but chemically isolated from resident melt. Up to 30 instances (n ≤ 30) of magma mixing by recharge and/or bulk assimilation of stoped wallrock blocks can occur in a single simulation; each recharge magma or stoped block has a unique user-defined composition and thermal state. Recharge magmas and stoped blocks hybridize (equilibrate) with resident melt, yielding a single new melt composition and temperature. MCS output includes major and trace element concentrations and isotopic ratios (Sr, Nd, Hf, Pb, Os, and O as defaults) of wallrock, recharge magma/stoped blocks, resident magma melt, and cumulates. The chemical formulae of equilibrium crystalline phases in the cumulate reservoir, wallrock, and recharge magmas/stoped blocks are also output. Depending on the selected rhyolite-MELTS engine, the composition and properties of a possible supercritical fluid phase (H2O and/or CO2) are also tracked. Forward modeling of theoretical magma systems and suites of igneous rocks provides quantitative insight into key questions in igneous petrology such as mantle versus crustal contributions to terrestrial magmas, the record of magmatism preserved in cumulates and exsolved fluids, and the chronology of RASFC processes that may be recorded by crystal populations, melt inclusions, and whole rocks. Here, we describe the design of the MCS software that focuses on major element compositions and phase equilibria (MCS-PhaseEQ). Case studies that involve fractional crystallization, magma recharge + mixing, and crustal contamination of a depleted basalt that resides in average upper crust illustrate the major element and phase equilibria consequences of these processes and highlight the rich array of data produced by MCS. The cases presented here, which represent an infinitesimal fraction of possible RASFC processes and bulk compositions, show that the records of recharge and/or crustal contamination may be subtle and are not necessarily those that would be predicted using conventional intuition and simple mass balance arguments. Mass and energy constrained thermodynamic tools like the MCS quantify the open-system evolution of magmas and provide a systematic understanding of the petrology and geochemistry of open system magmatic processes. The trace element and isotope MCS computational tool (MCS-Traces) is described in a separate contribution (part II).

中文翻译：

---

使用岩浆室模拟器 (MCS) 诊断开放系统岩浆过程：第 I 部分——主要元素和相平衡

岩浆室模拟器 (MCS) 是一种热力学工具，用于模拟岩浆系统的演化，这些系统在部分熔融或停止块的同化、岩浆补给 + 混合和分步结晶方面是开放的。MCS 可用于 PC 和 Mac。在 MCS 中，常驻岩浆、围岩和补给储层的多组分-多相复合系统的热、质量和成分演化通过严格的自洽热力学模型进行跟踪。再充电-同化（同化部分熔化或停止块）-分馏（RnASnFC；ntot ≤ 30）场景是通过使用与 Excel Visual Basic 界面耦合的流纹岩和 pMELTS 引擎系列最小化或最大化适当的热力学势来计算的。在 MCS 中，在等压冷却和结晶过程中，常驻岩浆与处于内部热力学平衡的围岩发生热相互作用。高于用户定义的渗透阈值的围岩部分熔体与常驻岩浆均质化（即达到化学势平衡）。形成的晶体成为累积储层的一部分，该储层保持热连接，但与常驻熔体化学隔离。在一次模拟中，最多可以发生 30 次 (n ≤ 30) 的岩浆混合实例（n ≤ 30）。每个补充岩浆或停止块都有一个独特的用户定义的成分和热状态。补充岩浆和停止块与驻留熔体混合（平衡），产生单一的新熔体成分和温度。MCS 输出包括主要和微量元素浓度和同位素比率（Sr、Nd、Hf、Pb、Os、和 O 作为默认值）的围岩，补充岩浆/停止块，常驻岩浆融化，并累积。还输出堆积储​​层、围岩和补给岩浆/停止块中平衡结晶相的化学式。根据所选的流纹岩-MELTS 发动机，还可以跟踪可能的超临界流体相（H2O 和/或 CO2）的组成和特性。理论岩浆系统和火成岩系列的正向建模提供了对火成岩学中关键问题的定量见解，例如地幔与地壳对陆地岩浆的贡献，在堆积和溶出流体中保存的岩浆活动记录，以及可能存在的 RASFC 过程的年表由晶体种群、熔体包裹体和整块岩石记录。这里，我们描述了 MCS 软件的设计，该软件侧重于主要元素组成和相平衡 (MCS-PhaseEQ)。案例研究涉及位于平均上地壳的枯竭玄武岩的分步结晶、岩浆补给 + 混合和地壳污染，说明了这些过程的主要元素和相平衡结果，并突出了 MCS 产生的丰富数据。这里介绍的案例代表了可能的 RASFC 过程和整体成分的极小部分，表明补给和/或地壳污染的记录可能是微妙的，不一定是使用传统直觉和简单的质量平衡论点可以预测的那些。质量和能量受限的热力学工具（如 MCS）量化了岩浆的开放系统演化，并提供了对开放系统岩浆过程的岩石学和地球化学的系统理解。微量元素和同位素 MCS 计算工具 (MCS-Traces) 在单独的贡献（第二部分）中进行了描述。